Impact of primordial black holes on the formation of the first stars and galaxies

TL;DR

This study investigates how primordial black holes (PBHs) influence early star and galaxy formation through simulations and analysis, considering their roles in structure acceleration and gas heating.

Contribution

It combines semi-analytical methods and cosmological simulations to assess PBHs' effects on the formation of the first stars and galaxies, highlighting their potential roles as seeds for massive structures.

Findings

Stellar-mass PBHs likely have minor impact on primordial star formation.

PBHs can alter properties of early star-forming halos and clouds.

Supermassive PBHs may serve as seeds for massive galaxy formation.

Abstract

Recent gravitational wave (GW) observations of binary black hole (BH) mergers and the stochastic GW background have triggered renewed interest in primordial black holes (PBHs) in the stellar-mass ($\sim 10 - 100\ \rm M_\odot$) and supermassive regimes ($\sim 10^7 - 10^{11}\ \rm M_\odot$). Although only a small fraction ($\lesssim 1\%$) of dark matter (DM) in the form of PBHs is required to explain such observations, these PBHs may play important roles in early structure/star/galaxy formation. In this chapter, we combine semi-analytical analysis and cosmological simulations to explore the possible impact of PBHs on the formation of the first stars and galaxies, taking into account two (competing) effects of PBHs: acceleration of structure formation and gas heating by BH accretion feedback. We find that the impact of stellar-mass PBHs (allowed by existing observational constraints) on primordial star formation is likely minor, although they do alter the properties of the first star-forming halos/clouds and can potentially trigger the formation of massive BHs, while supermassive PBHs serve as seeds of massive structures that can explain the apparent overabundance of massive galaxies in recent observations. Our tentative models and results call for future studies with improved modeling of the interactions between PBHs, particle DM, and baryons to better understand the impact of PBHs on early star/galaxy/structure formation and their imprints in high-redshift observations.